Hydraulic fracturing is a well stimulation technique that involves injecting a fracturing fluid into subterranean formations at rates and pressures sufficient to rupture the subterranean formation to produce or widen compressed flow conduits, that is fissures, cracks, natural fractures, faults, lineaments and bedding planes. Viscoelastic surfactants (VES) fluids are often used in oilfield applications, such as hydraulic fracturing. Specifically, the VES fluids exhibit both elastic behavior and viscous behavior due to the micelles structure formed under different conditions. When the VES fluid is subjected to shear stress, for example, by a pump, the VES fluid is shear thinned to produce a low viscosity fluid, which is easier to pump. When the shear stress is stopped, the VES fluid returns to a higher viscosity condition. Because the fracturing fluid contains a proppant that keeps an induced hydraulic fracture open after the pressure is released, a higher viscosity enables the VES fluid to suspend and transport the proppant into the fracture.
Regarding the surfactant aggregation, the VES fluid includes wormlike micelles that become entangled to form a 3-dimensional (3D) viscoelastic gel, limiting mobility of solution molecules, for example water. Due to the advantages, such as low subterranean formation damage, good proppant suspending and carrying ability, good compatibility with brine and produced water, the VES fluids have been widely used in oilfield operations including fracturing, completion, acidizing, sand control, water shut-off, etc.
However, current viscoelastic fluid systems have a temperature limit of approximately 250 degrees Fahrenheit (° F.) beyond which the fluid viscosity is unsuitable for fracturing application.